When arranging an intermediate casing in a conductor pipe, or when arranging a production casing in an intermediate casing, an annular isolation packer is set in the annular space to prevent the fluid from the surrounding formation from flowing into the annular space. The pressure integrity between two tubulars is very important and the annulus between them is tested on a regular basis. If the pressure integrity is broken, the operator can no longer prove well control, and the well is shut down.
Therefore, it is very important that these annular packers seal off the formation pressure. However, it is very difficult to leak-test the packer without at the same time breaking the pressure integrity, as the formation or cement is on one side, and thus, injection of a tracer into the formation fluid will break the integrity since the casing is then also penetrated.